1. Field of the Invention
2. Description of the Prior Art
As shown in FIG. 8, a starter (a coaxial type starter) is known, in which an solenoid switch 200, an overrunning clutch 300 with a pinion 30P adapted to engage with a ring gear 500, a plunger (a movable iron-core) and the like are coaxially arranged relative to an output shaft 100.
This type of starter operates as shown below.
That is, when current flows to an exciting coil of the solenoid switch 200, the plunger is attracted to a core of the solenoid switch. After a little when the plunger is attracted and starts to move, a movable contact contacts a stationary contact and electric power is supplied to a DC motor and the output shaft 100 is turned via a shaft (a motor shaft), a reduction mechanism and the like. Then, the overrunning clutch 300, which is spline-connected to the output shaft 100, moves toward the ring gear 500, and the pinion 30P meshes with the ring gear 500 and an engine is started.
In a starter as shown in FIG. 8, a pinion return coil spring 510 is arranged coaxially relative to the output shaft. This pinion return coil spring 510 is compressed when the pinion 30P is moved in the direction to mesh with the ring gear 500 and gives the depressing force to the end of the pinion 30P to return the pinion 30P to the original position when power is no longer applied to the exciting coil. Namely, the pinion return coil spring 510 is held in the axial direction between a washer 520 provided in front of the pinion 30P and a rear end surface 530e of a stopper 530 mounted to protect the pinion 30P from moving in the forward direction of the starter by a stop ring 540.
In a starter disclosed in Japanese Laid-Open Patent Application No. Hei 9-195902, the pinion return coil spring 510 is held in the axial direction between the pinion 30P and a collar 550 mounted to prevent the pinion 30P from moving in the forward direction of the starter by the stop ring 540.
The pinion return coil spring 510 uses generally a spring that is made of such a material as a piano wire, etc. and has the section in almost circular shape.
In the conventional starter shown in FIG. 8, the pinion return coil spring 510 is simply held in the axial direction between the washer 520 and the stopper 530. In a conventional starter shown in FIG. 9, the pinion return coil spring 510 is also simply held in the axial direction between the top surface of the pinion 30P and the collar 550. In this structure, the pinion return coil spring became eccentric in the radial direction, interfered with the output shaft 100, was shaved and damaged in some cases.
Further, in FIG. 8, when an engine is started and the ring gear 500 drives the pinion 30P, that is, in the overrun state, relative rotation is produced between the pinion 30P and the output shaft 100. However, if sliding between the washer 520 and the pinion 30P is not effected and three of them including the pinion return coil spring 510 rotate together, the other end of the pinion return coil spring 510 and the stopper 530 also rotate together with relative rotation. When the winding direction (the clockwise or counterclockwise winding) of the pinion return coil spring 510 is the same direction as that of the pinion 30P, the pinion return coil spring 510 might be rolled in the inner peripheral side and could be broken in the worst case. Further, in FIG. 9, when the direction of winding of the pinion return coil spring 510A is the same direction as that of rotation of the pinion 30P, sliding between the pinion 30P and the pinion return coil spring 510 is not effected and they rotate together, the same problem as seen in FIG. 8 will be produced.
In FIG. 8, when the winding direction of the pinion return coil spring 510 and the rotating direction of the pinion 30P differ, the pinion return coil spring 510 is expanded to the outer portion by centrifugal force or the washer 520 is caught by the end of the pinion return coil spring 510 and tries to unwind the spring (in FIG. 9, the top surface of the pinion 30P is caught by the end of the pinion return coil spring 510) and therefore, the pinion return coil spring 510 might be broken by centrifugal force applied to it in the worst case.
Further, in FIG. 8, when the portion between the washer 520 and the pinion 30P is rusted, the movement of the pinion return coil spring 510 becomes further worse and the probability of the breakage of the pinion return coil spring 510 becomes very high. In FIG. 9, the same also applies if the portion between the pinion return coil spring 510 and the pinion 30P is rusted.